1. Field of Invention
The invention relates to a light source and a method for fabricating the same. More particularly, the invention relates to a planar light source with high brightness and a method for fabricating the same.
2. Description of Related Art
Recently, the liquid crystal display (LCD) has gradually replaced the cathode ray tube (CRT) display and becomes a mainstream display in the market. However, the liquid crystal display panel cannot emit light by itself, so a back light module must be disposed below the liquid crystal display panel for providing a light source, so as to display pictures. As the light source provided by the back light module for the liquid crystal display panel is a surface light source, if a planar light source with high brightness is directly adopted for providing a surface light source for a liquid crystal display panel, the display brightness of the LCD can be enhanced.
FIG. 1 is a partial sectional view of a conventional planar light source. Referring to FIG. 1, a planar light source 100 includes an upper substrate 110, a lower substrate 120, electrode pairs 130, a dielectric layer 140, a phosphor layer 150, and ribs 160. The electrode pairs 130 are disposed on the lower substrate 120, and the dielectric layer 140 covers the electrode pairs 130. The phosphor layer 150 is disposed between the electrode pairs 130 and the surface of the upper substrate 110 facing to the lower substrate 120. The ribs 160 separate a plurality of discharge spaces 170 between the upper substrate 110 and the lower substrate 120, wherein the discharge spaces 170 are filled with discharge gas 180.
The illumination principle of the planar light source 100 is to generate high-energy electrons by the high voltage difference between the electrode pairs 130, and then hit the discharge gas 180 with the generated high-energy electrons, so as to generate so-called plasma. Afterward, activated atoms in an excited state in the plasma will emit ultraviolet rays when returning to the ground state, and then the emitted ultraviolet rays further activate the phosphor layer 150 in the planar light source 100 for emitting visible light.
With respect to the planar light source, how to enhance the illumination brightness has become one of the key issues under research and development. Moreover, the method for generating the high voltage difference described above adopts the electrode pairs 130 to accumulate charges through the dielectric layer 140 thereon, thereby activating the discharge gas 180 to generate plasma. As such, the shape of the dielectric layer 140 may affect the output of the plasma as well as the efficiency for generating ultraviolet rays, thereby affecting the illumination brightness of the planar light source.